GB1565160A

GB1565160A - Abrasive wheels

Info

Publication number: GB1565160A
Application number: GB5369977A
Authority: GB
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1977-12-23
Filing date: 1977-12-23
Publication date: 1980-04-16

Description

(54) ABRASIVE WHEELS (71) We, HONDA GIKEN KOGYO KABUSHIKI KAISHA, a body Corporate existing under the laws of Japan, of 27-8, Jingumae 6-Chome, Shibuya-Ku, Tokyo To, Japan, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to abrasive wheels for use in grinding machines. Known types of such wheels utilise a wheel body formed of a matrix material to which are fixed hard grains such as diamond or cubic crystals of boron nitride. As a rule such grains are applied in multiple layers to a certain thickness on the outer peripheral surface of the matrix material, such material being in an appropriate wheel shape of standard form and the resulting wheel is thereafter corrected or adjusted for wheel balance and circularity.Accordingly such an abrasive wheel has several disadvantages. Firstly the utmost care has to be taken in handling the wheel at the time of its adjustment for wheel balance and circularity because of the layers of grains thereon. Secondly, since expensive abrasive grains have to be coated to a relatively heavy thickness its manufacturing cost will be high. Thirdly, the coating of the grains tends to be non-uniform which produces an unbalanced condition during wheel rotation and also deflection of the abrasive surface from a circular path during rotation.

Fourthly, truing and dressing of the wheel are inevitably required although these operations are not always practical or well established in many factories and in particular they are almost impossible to carry out when the abrasive wheel is of a rather complicated shape. The truing and dressing operations require special apparatus in the manufacturing stages of the abrasive wheel.

There is also difficulty in mounting the wheel on the grinding machine. Finally there are the dangers that the expensive grains tend to be dulled during the processes of balancing and truing.

According to one aspect of the present invention an abrasive wheel comprises a wheel body which body is balanced and has a substantially true circular circumference, a tapered fitting provided on the body for mounting the wheel onto a corresponding taper on a grinding machine, and a single layer of abrasive grains formed on the outer peripheral surface of the wheel body. The fitting may be a tapered hole or a tapered boss.

Preferably a plurality of linear grooves are formed on the outer peripheral surface of the wheel body. the abrasive grains not continuing into the bottoms of the grooves.

According to another aspect of the present invention a method of forming an abrasive wheel having a tapered fitting for mounting onto a corresponding taper on a grinding machine comprises the steps of balancing the wheel, providing it with a substantially true circular circumference and subsequently forming a single layer of abrasive grains on the outer peripheral surface of the wheel. Preferably the abrasive grains are applied during an electroplating process.

For example, the wheel may be mounted in an electroplating chamber and abrasive grains are circulated through the chamber during the electroplating process.

The invention may be carried into practice in a number of ways but certain specific embodiments will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a side elevation partly in section of an abrasive wheel having a tapered centre hole; Figure 2 is a similar view of an alternative embodiment having a tapered boss; Figure 3 is an enlarged diagrammatic cross sectional view showing the bonding between abrasive grains and the matrix material for the wheel; Figure 4 is a side elevation of an abrasive wheel having grooves which extend parallel to the direction of the rotational axis thereof; Figure 5 is an enlarged partial cross sectional view showing how abrasive grains are coated in the region of a groove of the matrix material of the wheel; Figure 6 is a side elevation of a further embodiment;; Figure 7 is a view of another embodiment for grinding the inner bore of a workpiece, and Figure 8 is a longitudinal cross sectional view of a device for coating abrasive grains on the outer peripheral surface of the abrasive wheel.

Figure 1 shows an abrasive wheel for grinding the outer surface of the workpiece which comprises a body 1 which is first subjected to wheel balancing and surface treatment in order to ensure surface circularity. On the outer peripheral surface of the body is formed a single layer of abrasive grains 2 (see Figure 3) by means of a plating method to be described in detail with reference to Figure 8. The body has a centre hole of tapered form for mounting the wheel onto a grinding machine Figure 2 illustrates an alternative embodiment in which the body 1 of the wheel has a tapered boss 5 to be secured to a tapered centre hole formed on the end of a shaft 6 of the grinding machine.

Figure 4 shows an aternative embodiment in which a wheel body is provided with a plurality of grooves on its external surface prior to the application of the abrasive layer. The grooves extend parallel to the direction of the rotational axis of the wheel, and have their edges curved with a chamfer, and a single layer of abrasive grains 2 is formed on the outer peripheral surface portions as well as in the edge portions of the grooves as indicated at 8 in Figure 5.

This increases the bonding strength of the abrasive grains in the region of the edge portions of the grooves.

Formation of grooves between adjacent layers 2 of abrasive grains contributes to smooth flow of cooling liquid during grinding operations and also provides a path for the escape of chips from the workpiece. This avoids loading of chips between the work and the wheel. The number of grooves can vary according to requirements.

Figure 6 shows an alternative embodi ment in which grooves extending in straight lines are formed of diamond shapes, or criss cross fashion on the surface of the wheel matrix.

Figure 7 shows an abrasive wheel for grinding the inner bore of a workpiece in which straight line grooves are formed radially so as to extend outwards from the tip of the bulbous head of the matrix wheel 9.

Figure 8 shows one embodiment of a device for coating the abrasive grains on the outer peripheral surface of the wheel body.

In this embodiment a casing 11 has a feeding port 12 and a discharge port 13 for plating liquid. A screen 15 having a mesh size that does not permit passage of the abrasive grains therethrough is provided at the boundary portion of the discharge port 13 and a matrix accommodating chamber 14.

The wheel body 1 is secured to a shaft 16 within the chamber 14. In this case the wheel body is subjected to a process for electrical insulation on both upper and lower surfaces thereof leaving clear the outer peripheral surface thereof. A gap 17 is provided between the outer peripheral surface of the wheel body 1 and the inner wall surface of the casing 11. Between a base 18 for the wheel body supporting shaft 16 and a partition screen 19 (of the same material as the screen 15) positioned at the feeding port 12 for the plating liquid, there is formed a storage chamber 20 for abrasive grains 22.

This storage chamber is placed in communication with the chamber 14 by way of a plurality of bores 21 of such size that the abrasive grains may easily pass therethrough.

When plating liquid is fed from the feeding port 12 and circulated to the discharge port 13 through the wheel body accommodating chamber 14, the abrasive grains 22 in the grain storage chamber 20 are carried by the plating liquid, pass through the bores 21 and are led out into the wheel chamber 14 where the grains fill the entire space in the chamber including the gap 17.

During circulation of the plating liquid a plating film is gradually formed on the outer peripheral surface of the body and at the same time abrasive grains are secured firmly to the outer peripheral surface of the wheel body.

Upon completion of the above mentioned process, the wheel body 1 is removed from the chamber 14 and any excessive abrasive grains adhering to the outer peripheral surface of matrix may be removed, either by scraping or jets of water or other appropriate ways thereby to leave only a single layer of grains fixedly secured on the body surface.

Subsequently a plating process is given to the wheel body so as to imbed about 70/80% of the grain diameter in the outer peripheral surface of the wheel body thereby ensuring the bonding of a single layer of grains onto the body surface as shown in Figure 3. The reference number 23 in Figure 3 designates the plating layer just referred to.

By this method the wheel body, in advance of the application of grains, is precisely balanced and provided with true circularity and as consequence repair and reuse of the abrasive wheel is possible should the grains become dulled during use or fall off from the wheel surface. The repairing can be done in such a manner that the layer of abrasive grains is separated from the wheel together with the plated layer or the layers may be removed by an electrolytic method after which a new single layer of grains is formed on the outer peripheral surface of the body by means of the same process.

The wheels formed according to the invention have the following advantages.

Firstly since the abrasive surface consists of a single layer of grains the quantity of grains to be used can be small so that the overall cost of the wheel can be low in spite of using relatively expensive abrasive grains.

Secondly since the bonding strength between the abrasive grains and the wheel body is strong the falling off of abrasive grains from the wheel's surface can be reduced to the minimum, in contrast to known abrasive wheels having a plurality of grain layers wherein abrasive grains are mutually bonded together in multiple layers and the bonding strength among the abrasive grains has been found to be weaker than in the case of abrasive grains and wheel body according to the present invention.

Thirdly the fact that the abrasive grains are formed in a single layer on the outer peripheral surface of the wheel body provides a high precision product so that there is little or no deflection of the abrasive surface of the wheel during operation of the grinding machine. As a consequence there is no necessity for truing the wheel after the application of the grains and moreover the abrasive wheel can be formed to a complicated configuration without difficulty.

Furthermore, since there are spaced intervals between adjacent abrasive grains there tends to be no loading of chips and the like and there is no necessity for a dressing operation. Moreover, since neither a truing operation nor a dressing operation is required a corrective device for the abrasive surface which has previously been additionally provided in the grinding machine becomes unnecessary so that the cost of the grinding machine as a whole can be effectively reduced.

A further advantage is that after truing of the wheel body the tapering of a hole, or formation of a boss, for fitting the abrasive wheel onto the grinding machine can be carried out on the basis of the outer diameter whereby a highly precise tapered surface can be obtained and the abrasive wheel can be more readily fitted onto the grinding machine than is the case with conventional flange type abrasive wheels.

Moreover, the precision in its fitting onto the grinding machine is excellent.

Finally, since the wheel body can be used repeatedly the overall cost of the abrasive wheel can be effectively reduced.

WHAT WE CLAIM IS: 1. An abrasive wheel comprising a wheel body, which is balanced and has a substantially true circular circumference, a tapered fitting provided on the body for mounting the wheel onto a corresponding taper on a grinding machine, and a single layer of abrasive grains formed on the outer peripheral surface of the wheel body.

2. An abrasive wheel as claimed in Claim 1 in which the fitting is in the shape of a tapered hole.

3. An abrasive wheel as claimed in Claim 1 in which the fitting is in the form of a tapered boss.

4. An abrasive wheel as claimed in any one of the preceding claims in which a plurality of linear grooves are formed on the outer peripheral surface of the wheel body, the abrasive grains not continuing into the bottoms of the grooves.

5. An abrasive wheel as claimed in Claim 4 in which the edges of each of the grooves is chamfered arcuately.

6. An abrasive wheel as claimed in Claim 4 or Claim 5 in which the grooves extend parallel with the rotational axis of the body.

7. An abrasive wheel as claimed in any one of Claims 1 to 5 including a plurality of mutually criss crossed linear grooves formed on the outer peripheral surface of the body.

8. An abrasive wheel substantially as described herein with reference to Figures 1 and 3; 2 and 3; 4 and 5, 6 or Figure 7 of the accompanying drawings.

9. A method of forming an abrasive wheel having a tepered fitting for mounting onto a corresponding taper on a grinding machine comprising the steps of balancing the wheel, providing it with a substantially true circular circumference and subsequently forming a single layer of abrasive grains on the outer peripheral surface of the wheel.

10. A method as claimed in Claim 9 in which the abrasive grains are applied during an electroplating process.

11. A method as claimed in Claim 10 in which the wheel is mounted in an electroplating chamber and abrasive grains are circulated through the chamber during the electroplating process.

12. A method as claimed in Claim 10 or Claim 11 in which any excess of grains are removed to leave the single layer.

13. A method as claimed in Claim 12 in which the excess of grains are removed by scraping.

14. A method as claimed in Claim 12 in

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. By this method the wheel body, in advance of the application of grains, is precisely balanced and provided with true circularity and as consequence repair and reuse of the abrasive wheel is possible should the grains become dulled during use or fall off from the wheel surface. The repairing can be done in such a manner that the layer of abrasive grains is separated from the wheel together with the plated layer or the layers may be removed by an electrolytic method after which a new single layer of grains is formed on the outer peripheral surface of the body by means of the same process. The wheels formed according to the invention have the following advantages. Firstly since the abrasive surface consists of a single layer of grains the quantity of grains to be used can be small so that the overall cost of the wheel can be low in spite of using relatively expensive abrasive grains. Secondly since the bonding strength between the abrasive grains and the wheel body is strong the falling off of abrasive grains from the wheel's surface can be reduced to the minimum, in contrast to known abrasive wheels having a plurality of grain layers wherein abrasive grains are mutually bonded together in multiple layers and the bonding strength among the abrasive grains has been found to be weaker than in the case of abrasive grains and wheel body according to the present invention. Thirdly the fact that the abrasive grains are formed in a single layer on the outer peripheral surface of the wheel body provides a high precision product so that there is little or no deflection of the abrasive surface of the wheel during operation of the grinding machine. As a consequence there is no necessity for truing the wheel after the application of the grains and moreover the abrasive wheel can be formed to a complicated configuration without difficulty. Furthermore, since there are spaced intervals between adjacent abrasive grains there tends to be no loading of chips and the like and there is no necessity for a dressing operation. Moreover, since neither a truing operation nor a dressing operation is required a corrective device for the abrasive surface which has previously been additionally provided in the grinding machine becomes unnecessary so that the cost of the grinding machine as a whole can be effectively reduced. A further advantage is that after truing of the wheel body the tapering of a hole, or formation of a boss, for fitting the abrasive wheel onto the grinding machine can be carried out on the basis of the outer diameter whereby a highly precise tapered surface can be obtained and the abrasive wheel can be more readily fitted onto the grinding machine than is the case with conventional flange type abrasive wheels. Moreover, the precision in its fitting onto the grinding machine is excellent. Finally, since the wheel body can be used repeatedly the overall cost of the abrasive wheel can be effectively reduced. WHAT WE CLAIM IS:

1. An abrasive wheel comprising a wheel body, which is balanced and has a substantially true circular circumference, a tapered fitting provided on the body for mounting the wheel onto a corresponding taper on a grinding machine, and a single layer of abrasive grains formed on the outer peripheral surface of the wheel body.

14. A method as claimed in Claim 12 in

which any excess of grains is removed by water jets.

15. A method as claimed in any one of Claims 9 to 14 including a further plating process to imbed 70 to 80% of the diameter of each grain in a single layer.